Go Back   Physics Help Forum > High School and Pre-University Physics Help > Kinematics and Dynamics

Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum

LinkBack Thread Tools Display Modes
Old Oct 14th 2009, 10:38 AM   #1
Junior Member
Join Date: Oct 2009
Posts: 4
Pulley on a slope.

I have the following question to answer. Can anyone please help.

A box of mass 150kg rests on a slope that is inclined to the horizontal by 35 degrees. The box is restrained so that it cannot slide down the incline but is free to move up the incline. At the top of the incline a pulley is mounted, over which a rope passes, which is attached to the box at one end and to a water tank at the other end. The water tank is free to move vertically such that if the tank moves down wards, the box moves up the incline. The pulley is positioned so that when the box is at rest the rope is inclined at an angle of 5 degrees above the slope (i.e. 40 degrees to the horizontal. You can assume that the pulley is frictionless, that the rope is light and inextensible and that the coefficent of friction between the surface of the incline and the box is 0.2.

(1) Determine the mass of water that must be added to the tank (assuming that the mass of the tank is 25kg) to just move the box up the incline.

(2) Assuming that the box is repositioned on the incline (same rope angle) and that 5 times the mass of water calculated in part 1 is instantaneously added to the tank, determine the acceleration of the box.

This is what i have so far...

Total R horizontal = T cos 5 - F - mgcos 35 = 0 (1)

Total R Perpendicular = Rn + T sin 5 - mgcos 35 = 0 (2)

F=u Rn (3)

For water tank

R vertical = T -Mwg = 0 (4)

Using 1&3 i can find T

T cos 5 - u Rn - mgsin 35 (5)

from 2 and 4

Rn + (mg sin 35 + u Rn / cos 5) sin 5 - mgcos 35 = 0

Is this the correct way in which to tackle this problem and if so any hints as to where to go with it now...

Thank you
JAW is offline   Reply With Quote
Old Oct 14th 2009, 09:36 PM   #2
Physics Team
Join Date: Feb 2009
Posts: 1,425
For (1), the following eqns hold

T = (25 + Mw) g

T cos 5= 150 sin 35 + 0.2 (150 cos 35 - T sin 5).

Find Mw

For (2),

Let T1 be the new tension and a be the accln

(25 + 5 Mw) g - T1 = (25 + 5 Mw) a

T1 cos 5 - [150 sin 35 + 0.2 (150 cos 35 - T sin 5)] = 150 a

Find a
physicsquest is offline   Reply With Quote

  Physics Help Forum > High School and Pre-University Physics Help > Kinematics and Dynamics

pulley, slope

Thread Tools
Display Modes

Similar Physics Forum Discussions
Thread Thread Starter Forum Replies Last Post
Friction coefficient and slope Johulus Kinematics and Dynamics 1 Aug 12th 2015 08:08 AM
Work along a slope wedam Kinematics and Dynamics 4 May 11th 2013 07:51 AM
Work done on a slope Alexrey Advanced Mechanics 2 Jun 5th 2009 08:04 AM
Physics - friction up a slope Intrusion Kinematics and Dynamics 1 Feb 20th 2009 06:26 PM
inclined slope, b degrees devanlevin Kinematics and Dynamics 1 Nov 27th 2008 07:24 PM

Facebook Twitter Google+ RSS Feed